I own a fretted six-string Modulus Quantum that I bought new in 1994. My bass has an alder body, quilted maple top, two Bartolini soapbars with a 9-volt NTMB preamp (volume, mix, bass, mid, and treb). In 1994, Modulus didn't equip Quantums with a truss rod. After nine years, the action of my bass is still quite low. With the maple top, its tone is very bright, yet full. The Barts and NTMB preamp can provide a wide variety of tones. I find my Quantum's tone includes a growl that I attribute to the graphite neck as it's similar to the modern-tone growl I experienced with a Steinberger I used to own. I string mine with DR stainless steel Lo-Riders and the B-string is excellent.
Aesthetically, I think a Quantum can be built as gorgeous as any bass out there. My bass has a black cherry velvet stain that is carried through in the graphite neck ($100 option). It's a stunner with the gold hardware. The six-string I have isn't exactly a light-weight bass though, so I use a 3.5" wide strap with it.
While I find my Quantum 6 to be a fantastic sounding, fantastic looking, fantastically playable (and I have relatively small hands) bass, my only complaint I have with it is due to the poor customer service I've received from Modulus. Their response to phone calls and emails has been quite disappointing. But, I still think I'd buy another Modulus bass because they really are that good.